Process to prepare pharmaceutical compositions containing vecuronium bromide and compositions produced thereby

ABSTRACT

The invention relates to a process for preparing a pharmaceutical preparation having neuromuscular blocking activity in a vial by dissolving vecuroniumbromide or an analogue thereof in water saturated with carbondioxide or an organic solvent, filling the solution thus obtained into the vial to provide therein the required unit dosage form of vecuronium bromide or an analogue thereof, removing the solvent, i.e. water or organic solvent in the vial by lyophilization or evaporation, and hermetically closing the vial. The invention also relates to a method of preparing an aqueous injection solution starting from said vial by dissolving the contents of the vial either in an amino acid solution of sufficient concentration so as to obtain a final physiological pH or in a pharmaceutically acceptable buffer system of pH 7 to 7.4.

This invention relates to a process for preparing a pharmaceuticalpreparation having neuromuscular blocking activity. The inventionparticularly relates to a process for preparing such a preparationcontaining as neuromuscular blocking agent a 16beta-monoquaternaryammonium derivative of a 2beta, 16beta-bis-piperidino-3alfa,17beta-dihydroxy-5alfa-androstane-3alfa, 17beta-diacylate.

From British Patent Nr. 1 138 605 it is known that the 2beta,16beta-bisquaternary ammonium derivatives of 2beta,16beta-bis-piperidino-3alfa. 17beta-dihydroxy-5alfa-androstane-3alfa,17beta-diacylates are highly active neuro-muscular blocking agents. Anexample of such a compound is pancurontumbromide (2beta,16beta-bis-piperidino-5alfa-androstane-3alfa, 17beta-diol 3alfa,17beta-diacetate 2beta, 16beta-dimethobromide).

In J. Med. Chem. 16, 1116 (1978) it is disclosed that not only suchbisquaternary derivatives, but also the corresponding 16-mono-quaternaryderivatives are interesting neuromuscular blocking agents. Thesemono-quaternary derivatives are even more interesting than thecorresponding bis-quaternary compounds because of their quicker onsetand shorter duration of action, thus offering under most surgicalconditions pronounced advantages, and because of their lack ofcardiovascular side-effects. A well-known example of a mono-quaternarycompound is vecuroniumbromide (2beta,16beta-bis-piperidino-5alfa-androstane-3alfa, 17beta-diol 3alfa,17beta-diacetate 16beta-methobromide), hereinafter referred to as "VB".

Generally, the quaternarizing group in the above-mentioned androstanecompounds is an alkyl, alkenyl or alkynyl group of up to 4 carbon atom,of which the methyl group is preferred. The counterion for the positivequaternary group may be any pharmaceutically acceptable organic orinorganic anion, such as methylsulphate, p-toluene-sulphonate andespecially the halides such as chloride, bromide and iodide, of whichbromide is preferred. The acyl group in 3alfa- and 17beta-position isderived from a lower aliphatic carboxylic acid having 1-6 carbon atomand is preferably the acetyl group.

The present invention is described herein with respect to VB. However,it should be noted that in the following disclosure any of theabovementioned 16-mono-quaternary analogues of VB may be substitited forVB without departing from the scope of the present invention.

According to the disclosure of EP-A-008824 VB decomposes almostimmediately when dissolved in water and hence cannot be used in aqueousinjection preparations. Neuromuscular blocking agents are mainly used insurgical treatments and are administered through injection of theiraqueous solution. For making stable injection preparations of VB it issuggested in EP-A-008824 to convert VB into a pharmaceuticallyacceptable acid addition salt thereof by reacting VB with apharmaceutically acceptable organic or inorganic acid, preferably awater soluble acid, e.g. hydrochloric acid, acetic acid, fumaric acid,citric acid.

According to the "Repertorium" (a review of information texts ofpharmaceutical specialite's registered in the Netherlands, edited byNefarma, the Dutch Phamaceutical Manufactures Association) thepreparation of VB (Norcuron®) consists of a vial containing alyophilized mixture of the acid addition salt of VB (4 mg or 10 NaCl(0.15 mmol), mannitol (24.5 mg) and a citrate or phosphate buffer. Forobtaining an injectable solution the contents of the vial should bedissolved in water for injection purposes (1 ml or 5 ml) giving anisotonic injection solution having a pH of 4. The injection solution isstable for 24 hours at room temperature in the light.

It is an object of the present invention to provide a new method forpreparing stable pharmaceutical preparations of VB for injectionpurposes.

The present invention comprises a method for preparing a stablepharmaceutical preparation containing VB characterized by the steps of

(a) dissolving VB in water saturated with carbondioxide or in an organicsolvent,

(b) filling the solution thus obtained into containers, e.g. vials, toprovide in each container the required unit dosage form of VB,

(c) removing the solvent, i.e, water or organic solvent, from eachcontainer by lyophilization or evaporation, and

(d) hermetically closing the container.

The special method according to the invention makes the extra step offirst converting VB into an acid addition salt thereof superfluous.

When in step (a) carbondioxide saturated water is used as the solvent,the temperature thereof should be within the range of from 0° C. to 25°C. and is preferably normal room temperature. Despite the presence ofwater VB surprisingly appears to be stable within the said temperaturerange, i.e. hydrolysis of VB to the corresponding 3-alfa-hydroxycompound does not substantially take place, as will be shown in theexamples which will follow hereinafter. The pH of the carbondioxidesaturated aqueous solution of VB is about 7.0, whereas the pH of ancarbondioxide free aqueous solution is within the range of from 8.5 to9.5.

When in step (a) an organic solvent is used for dissolving VB, saidsolvent can be selected from the group consisting of dichloromethane,choroform, acetone, ethanol, acetonitrile, and the like. In step (c) theorganic solvent is removed by evaporation without leaving any tracethereof.

From an aqueous solution of VB obtained in step (a) water is preferablyremoved by lyophilization or freeze-drying at a temperature of below-25° C., e.g. -30° C. Removal of water in this way in the form of icecan be performed in some hours, e.g 5 hours.

A big advantage of filling the vials with VB in the form of a solutionthereof (step (a)) is that the solution can be provided easily insterilized form, e.g. by simple filtration through an absolutefiltersystem (microporous filter, e.g. a Millipore® filter, such asMillidisk 0.22 μm hydrophilic filter) under nitrogen atmosphere. Afurther advantage of this way of filling the vials is that an accuratedosage in the vial can be provided, e.g. each vial can be filled with a1 ml aliquot of a solution containing 10 mg VB for providing vials eachcontaining 10 mg VB. Filling of the vials with VB in powder form isdifficult. Even micronized VB has poor theological properties (poorfree-flowing characteristics), so that filling each vial with the exactamount of VB, using e.g. the "screw filling" technique, is impossible.The required amounts of VB in the vials are not within the 95%confidence limit. Moreover, sterilization of VB in the solid form, e.g.a powder, my present problem. It will be necessary to sterilize withe.g. gamma-rays. All these problem with filling the vials with VB powderare avoided by filling the vials with a solution of VB and then removingthe solvent by lyophilization or evaporation according to methodswell-known for a person with average skill in the art of pharmaceuticaltechniques.

Before the lyophilization or evaporation step and for ease of furtheroperation each vial may receive a stopper cap, usually of a syntheticmaterial, that is placed on the top of the vial in a skew way, but doesnot close the vial. The vials are then quickly deep frozen by passing ona cold plate in a precooled lyophilization machine (-30° C.). Freezedrying commences immediately and after ascertaining complete evaporationof the liquid each vial is closed hermetically with the cap and the vialcap is fixed with a metallic ring-like cap in order to protect it fromaccidental opening

The vials obtained by the method according to the present invention andeach exactly containing the required amount of VB, e.g. 10 mg, can beused in clinical practice to produce skeletal muscular paralysis duringsurgical operations. Just prior to the use the vial is opened, therequired amount of aqueous injection solution for dissolving the VB isadded, e.g. 1 ml sterile water containing sodium chloride in asufficient amount so as to ascertain isotonicity with human plasma, andthe VB solution is then injected intravenously with a syringe. A VBsolution, containing e.g. 10 mg/ml, can also be administered byinfusion.

The aqueous solution of VB for injection obtained by the method ofreconstitution as described hereinabove can be checked for its contentsof VB and for its pH. The contents of VB is within the confidence limitaccepted for this purpose.

When according to the invention water saturated with carbondioxide hasbeen used as the solvent for preparing the VB preparation, the method ofreconstitution as described hereinabove results in an aqueous solutionof VB having a pH slightly exceeding the value 9 indicating that duringthe freeze drying step all carbondioxide has been removed.

Also, when according to the invention an organic solvent has been usedas the solvent for preparing the VB preparation, the method ofreconstitution as described hereinabove results in an aqueous solutionof VB having a pH slightly exceeding the value 9 indicating the presenceof pure VB in the solution.

The aqueous injection solution may be sterile water or physiologicalsaline.

Prior to lyophilization of the VB solution of the present inventionother pharmaceutical excipients may be added to obtain a consistentpowder after lyophilization.

The powder, obtained by lyophilization of a VB solution in carbondioxidesaturated water, may also be reconstituted prior to injection bydissolving the powder under aseptic conditions in a buffered solutionhaving a physiological pH of 7 to about 7.4. Preferred buffer system arephosphate buffers, but any pharmaceutical acceptable buffer system canbe used. Also, the lyophilized powder of VB can be dissolved insolutions of suitable amino acids such as glycine, L-serine or any otherpharmaceutically acceptable amino acid the like, having a concentrationso that the pH of the resulting injection solution does not exceed 7.5,e.g. 0.15M resulting in a pH of 7.45.

The invention will be illustrated by the following non-limitingexamples.

EXAMPLE 1 Stability of VB solutions with and without carbondioxide

Four solution were prepared as follows:

(1) 10 mg VB/ml carbondioxide free water, stored at 20° C., pH 9.0-9.5.

(2) As (1), but stored at 4° C.

(3) 10 mg VB/ml water saturated with carbondioxide, stored at 20° C., pH7.0. (The carbondioxide saturated water was obtained by slowly addingsolid carbondioxide to demineralized water, until the pH of the solutionreached a value between 3.5 and 4.5.)

(4) As (3), but stored at 4° C.

From these solutions TLC-analysis was performed immediately after thepreparations were made, after two hours, four hours, eight hours, 1 dayand further every day.

Next to these solutions, solutions containing 5, 10, 20 and 50 mg VB,respectively, in 100 ml dichloromathane were prepared and spotted nextto the above aqueous sample solutions. These dichloromethane solutionshad VB concentrations of 0.5%, 1%, 2% and 5%, respectively, of theaqueous sample solutions. Intensities of present secondary spots werecompared to these comparison solutions. The detection limit was 0.5%

The results are summarized in Table 1 below.

                  TABLE I                                                         ______________________________________                                                 Without          With                                                         carbondioxide    carbondioxide                                                4° C.                                                                       20° C.                                                                             4° C.                                                                         20° C.                                Lapsed time                                                                              (% VB present in the solution)                                     ______________________________________                                        0 hr       100    100         100  100                                        2 hr       70     60          >99  >99                                        4 hr       30     20          >99  >99                                        8 hr       20     10          >99  >99                                        1 day      <10    <10         >98  >98                                        2 days     <10    <10         >98  >98                                        3 days     <10    <10         >98  >98                                        5 days     <10    <10         >98  >98                                        9 days     <10    <10         >98  >98                                        ______________________________________                                    

From these results it is clear that carbondioxide containing aqueoussolutions of VB are very stable for at least 9 days.

EXAMPLE 2 Preparation of 1 ml vials each containing 10 mg VB

a) Preparation with carbondioxide saturated water as the solvent

To sterile water about 30 g of carbondioxide was added in the form ofcarboglace, with continuous stirring (500 rpm). Under sterile conditions10 g of VB was dissolved in 1000 ml of the water saturated withcarbondioxide gas. Immediately after the dissolution the solution waspassed under nitrogen atmosphere through an absolute filtering system,i.e. filtered through a Millipore™ filter (Millidisk 0.22 μm hydrophilicfilter). The filling of the vials with the filtered solution wasperformed immediately thereafter and each vial was accurately filledwith 1 ml of the solution. Each vial received a synthetic stopper capthat was placed in a skew way on the top of the vial, but did not closethe vial. The vials were quickly frozen by passing on a cold plate in aprecooled lyophilization machine (-30° C.). Freeze drying commencedimmediately and after ascertaining total evaporation of the liquid, thevials were closed hermetically and the vial cap was fixed with ametallic ring-like cap in order to protect it from accidental opening.

After the freeze drying process the amount of VB in the vial was checkedby dissolving the contents of the vial in water, whereafter the amountof VB in the solution was determined. An amount of almost exactly 10 mgwas found. In addition the pH of the solution was measured and found tobe slightly above 9, indicating that the vial did not contain anycarbondioxide, but only pure VB.

b) Preparation with acetonitrile as the solvent

To an accurately weighed portion of VB (10 g) was added acetonitrile anddissolved with the aid of a short duration of ultrasonic waves.Acetonitrile was added until the solution reached a final volume of 1liter. The solution obtained in this way was passed through an absolutefilter of 0.2 μm pore size for sterilization.

The filter system used was a Sartorius PTFE filter system (SM11807) of0.2 μm pore size, pre-autoclaved at 134° C.

After the filtration step an accurately measured volume of 1 ml of thatsolution of VB was transferred to a vial and lyophilized at -30° C.,after which the vial was hermetically closed.

Analysis of the VB in the vial showed clearly that the amount ofremaining acetonitrile was well below the 100 ppm level.

The gas chromatographic conditions used were as follows: stationaryphase: Chromosorb 80-100; carrier gas: helium; flow: 30 ml/min;temperature: 150° C.

EXAMPLE 3 Stability of aqueous injectable VB solutions afterreconstitution from lyophilised carbondioxide saturated aqueous VBsolutions

The following solutions (10 ml) were prepared from 1 mg VB which wasobtained by lyophilisation of a carbondioxide saturated aqueuos solutionof VB according to the method of Example 2a)

a) Phosphate buffer, pH 7.4

b) L-serine, 0.15M

c) Glycine, 0.15M

d) Water

The results of the stability determinations are summarized in Table 2below

                  TABLE 2                                                         ______________________________________                                        Solution    a)     b)         c)   d)                                         Time (hr)   (% VB present in the solution)                                    ______________________________________                                        0           100    100        100  100                                        1           100    100        100  60                                         2           100    100        100  30                                         4            98     98         98  20                                         8            97     95         95  10                                         ______________________________________                                    

The results indicate an excellent stability with solutions a), b) and c)according to the invention.

I claim:
 1. A method for preparing a stable pharmaceutical preparationcontaining vecuronium bromide comprising:dissolving vecuronium bromidein water saturated with carbon dioxide to obtain a solution; andlyophilizing the solution to provide a stable pharmaceutical preparationof vecuronium bromide.
 2. The method as claimed in claim 1, wherein,prior to lyophilization, the solution is filled into one or morecontainers such that each container holds an effective unit dosage ofvecuronium bromide.
 3. The method as claimed in claim 2, wherein, afterlyophilization, another container holding an effective amount of acarrier for an injectable formulation is combined into a kit with eachof the one or more containers holding effective unit dosages ofvecuronium bromide.